An electronic module is a highly-integrated component, which comprises one or more circuits monolithically integrated into a multi-layer substrate and fulfills various functions, in the terminal device of a mobile communication system, for example.
An electronic module can, for example, perform the function of an antenna circuit, a duplexer, a diplexer, a coupler, etc.
In addition to the integrated circuits, a module can contain one or more chip components as well as discrete circuit elements or components, which are disposed with the integrated circuit elements on the upper side of the multi-layer substrate.
It is frequently necessary to obtain a symmetrical signal at the output end of a chip component. To this end, either a balun can be integrated directly into the structure of the chip component, or a chip component having asymmetrical inputs and outputs and a downstream balun comprising discrete individual elements can be used. Such a balun can be executed as a compact, individual component.
To achieve a higher degree of integration, it is possible to arrange the chip component having upstream and downstream functional units on a shared dielectric substrate. In this manner, front end modules for time-duplexed systems such as GSM900/1800/1900 can be obtained, for example, when SAW filters (SAW=surface acoustic wave) are disposed on a multi-layer ceramic substrate together with the circuit elements of an antenna circuit. In this regard, the circuit elements of the antenna circuit can be partially integrated in the multi-layer substrate.
To achieve optimal signal transmission in the range of the pass band, it is necessary that the output impedance of a chip component be perfectly adjusted to the input impedance of the subsequent stage and/or that the input impedance of a chip component be perfectly adjusted to the output impedance of the upstream stage. Thus, to allow for their adjustment to their circuit environment, the chip components require an electric adjustment network. Such a network can comprise inductances, capacitances and delay lines, and its principal purpose is to adjust the impedance of a component to the external environment. It is known that an adjustment network can be executed, wherein the chip component, together with the discrete individual components, is soldered to a printed circuit board.
It is known that an SAW component having a multi-layer carrier substrate (made of ceramics, for example), which comprises integrated adjustment elements, can be attached and electrically connected by means of a flip-chip array or by means of wire bonding. See, for example, document U.S. Pat. No. 5,459,368. In addition to one or more SAW chips, additional passive or active, discrete circuit elements can be disposed on the upper side of the carrier substrate. However, the production of such components is complex and expensive, because SAW chips and/or so-called circuit elements are electrically connected with the carrier substrate by means of various connection methods.
If, for example, a chip component is connected in a reception branch in front of one or between two LNAs (low noise amplifier), the terminal impedance values that occur usually range between 50 and 200 Ohm. If the impedances of the upstage and downstage stages are known, it is essentially possible to execute the chip component in such a way that its input and/or output impedances correspond to the required values. In previously known chip components, the entire component had to be completely redeveloped for each application with the predetermined input and/or output impedance (e.g., 25, 50, 200 Ohm).
However, the range of available terminal impedances for components is often limited (especially in the case of SAW components).
External impedance converters equipped with discrete individual components can also be used. In the latter case, this results in an increase in space requirements. In addition, the reliability of the overall design suffers as a result of the required connection points.